On Emacs 23 you will need to get package.el
yourself or install manually by placing clojure-mode.el on your load-path
and requireing it.

Clojure Test Mode

This source repository also includes clojure-test-mode.el, which
provides support for running Clojure tests (using the clojure.test
framework) via nrepl.el or SLIME and seeing feedback in the test
buffer about which tests failed or errored. The installation
instructions above should work for clojure-test-mode as well.
(nrepl.el support is still in progress.)

Once you have a repl session active, you can run the tests in the
current buffer with C-c C-,. Failing tests and errors will be
highlighted using overlays. To clear the overlays, use C-c k.

You can jump between implementation and test files with C-c t if
your project is laid out in a way that clojure-test-mode expects. Your
project root should have a src/ directory containing files that
correspond to their namespace. It should also have a test/ directory
containing files that correspond to their namespace, and the test
namespaces should mirror the implementation namespaces with the
addition of "-test" as the suffix to the last segment of the namespace.

So my.project.frob would be found in src/my/project/frob.clj and
its tests would be in test/my/project/frob_test.clj in the
my.project.frob-test namespace.

Paredit

Using clojure-mode with paredit is highly recommended. It is also
available using package.el from the above archive.